#include<bits/stdc++.h>
#define int long long
#define endl '\n'
#define ph push_back
#define pp pop_back
using namespace std;

const int N=1e5+5;
int n,k,a[N],b[N];

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cin>>n>>k;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++)
    {
        int u=i%n+1,v=(i+n-2)%n+1;
        b[i]=(!a[i])+(!a[u])+(!a[v]);
    }
    int ans=3*n;
    for(int i=1;i<=k;i++) ans-=b[i];
    cout<<ans<<endl;
    return 0;
}